SW6090902_HISTORICAL FILE_20091102

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
HISTORICAL FILE
❑l COMPLIANCE EVALUATION INSPECTION
DOC DATE
C&
YYYYMMDD

F;
M
NC®ENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
November 2, 2009
I
Camden Ventures, LLC
Mr. Charles A. Gore, President.
5135 Morganton Road .
Fayetteville, NC 28314 -
Subject: Stormwater Permit No.ISW6090902 II' CEC Q Ill 204
Camden Wood Subdivision, Section 3 . p
Overall Low Density Residential Subdivision with
Pockets of High Density n(ogiCE
Cumberland County
Dear Mr. Gore:.'
The Stormwater Permitting Unit received a complete Stormwater Management Permit Application for Camden
Wood Subdivision, Section 3 on October 30, 2009. Staff review of the plans and specifications has determined
that the project, as proposed, will comply with the Stormwater Regulations set forth in Title 15A NCAC 2H.1000
and Session Law 2006-246. We are forwarding Permit No. SW6090902, dated November 2, 2009, for the
construction, operation and maintenance of the subject project and the stormwater BMPs.
I
This permit shall be effective from the date of issuance until November 2, 2019, and shall be subject to the
conditions and limitations as specified.therein. Please pay special attention to the Operation and Maintenance
requirements in this permit. Failure to,establish an adequate system for operation and maintenance of the
stormwater management system will result in future compliance problems.
If any parts, requirements, or limitations contained in this permit are unacceptable, you have the right to request .
an adjudicatory hearing upon written request within thirty (30) days following receipt of this permit. This request
must be in the form of a written petition, conforming to Chapter 150B of the North Carolina General Statutes, and.
filed with the Office of Administrative Hearings, P.O. Drawer 27447, Raleigh, NC 27611-7447. Unless such.
demands are made this perimit shall be final and binding.
If you have any questions, or need additional information concerning this matter, please contact Cory. Larsen at
[phone], or cory.la�[e-mail].
Sincerely,..
For Coleen H. Sullins
I
CC: iFayetteville Regional 0 fice
Central Files
SPU Files
Wetlands and Stormwater Branch One L, -
.1617 Mail Service Center, Raleigh, North Carolina 2769 -16V 1� Q]e �'$-olind.
. Location: 512 N. Salisbury : Raleigh, North Carolina r S604 _ Natimal�y
' Phone:[phone] FAX:919.807b4941 Customer Service:l-877-623-fi748� � � � [-i L
Internet m"v.nmaterquality.org-
An Equal Opportunny Affirmative Action Employer

State Stormwater Permit
Permit No. SW6090902
STATE OF NORTH CAROLINA
DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WATER QUALITY
STATE STORMWATER MANAGEMENT PERMIT
OVERALL LOW DENSITY SUBDIVISION DEVELOPMENT
WITH HIGH DENSITY POCKET
C�C 4 2(9
In accordance with the provisions of Article 21 of Chapter 143, General Statutes of North
Carolina as amended, and other applicable Laws, Rules, and Regulations
PERMISSION IS HEREBY GRANTED TO
Camden Ventures, LLC
Camden Wood Subdivision, Section 3
Fallberry Drive, Fayetteville, NC, Cumberland County
FOR THE
construction, operation and maintenance of one wet detention pond(s) in compliance with
the provisions of Session Law 2006-246 and 15A NCAC 2H .1000 (hereafter referred to as
the "stormwaterrules'l and the approved stormwater management plans and specifications
and other supporting data as attached and on file with and approved by the Division of
Water Quality and considered a part of this permit.
This permit shall be effective from the date of issuance until November 2, 2019 and shall be
subject to the following specified conditions and limitations:
I. DESIGN STANDARDS
1. This permit is effective only with respect to the nature and volume of stormwater
described in the application and other supporting data.
2. The overall tract built -upon area percentage for the project must be maintained at
17% per the requirements of Session Law 2006-246 of the stormwater rules. This
project is permitted for a maximum of 129,373 square feet of BUA.
3. The stormwater systems proposed to treat the runoff generated by the designated
high density areas have been approved for the management of stormwater runoff as
described in Section 1.6 on page 3 of this permit.
4. The subdivision is permitted for 16 lots, each allowed a maximum of 3,100 square
feet of built -upon area.
5. The low density portions of this project will maintain a minimum 30 foot wide
vegetated buffer between all impervious areas and surface waters.
6. Within the low density portions of the permitted project, the only runoff conveyance
systems allowed will be vegetated conveyances such as swales with minimum side
slopes of 3:1 (H:V) as defined in the stormwater rules and as shown on the approved
plan.
Page 1 of 7

State Stormwater Permit
Permit No. SW6090902
The following design elements have been permitted for this wet detention pond
stormwater facility, and must be provided in the system at all times.
a.
Drainage Area, acres:
8.83
Onsite, ftZ:
322,344
Offsite, ftZ:
62,291
b.
Total Impervious Surfaces, ftZ:
129,373
Lots at 3,100 ftZ:
49,600
Roads/Parking, ftZ:
59,463
Other, ftZ:
11,010
Offsite, ftZ:
9,300
c.
Average Pond Design Depth, feet:
3.7.
d.
TSS removal efficiency:
90%
e.
Design Storm:
1.01,
f.
Permanent Pool Elevation, FMSL:
169.00
g.
Permitted Surface Area @PP, ftZ:
12,353
In.
Permitted Storage Volume, ft3:
11,306 at temporary pool
i.
Storage Elevation, FMSL:
169.67
j.
Predevelopment 1 year 24 hour:
0.20 cfs
k.
Post development 1 year 24 hour:
0.05 cfs
I.
Controlling Orifice:
1.5"0 pipe
m.
Permanent Pool Volume, ft3:
46,038
n.
Forebay Volume, ft3:
9,699
o.
Receiving Stream / River Basin:
Rockfish Creek / Cape Fear
p.
Stream Index Number:
18-31-(18)
,q.
Classification of Water Body:
"B"
II. SCHEDULE OF COMPLIANCE
1. No homeowner/lot owner/developer shall fill in, alter, or pipe any drainage feature
(such as swales) shown on the approved plans as part of the stormwater,
management system without submitting a revision to the permit and receiving
approval from the Division.
The permittee is responsible for verifying that the proposed built -upon area for the
entire lot does not exceed the maximum allowed by this permit. Once the lot transfer
is complete, the built -upon area may not be revised without approval from the
Division of Water Quality, and responsibility for meeting the built -upon area limit is
transferred to the individual property owner.
3.. If an Architectural Review Board or Committee is required to review plans for
compliance with the BUA limit, the plans reviewed must include all proposed built -
upon area. Any approvals given by the Board do not relieve the homeowner of the
responsibility to maintain compliance with the permitted BUA limit.
The Director may notify the permittee when the permitted site does not meet one or
more of the minimum requirements of the permit. Within the time frame specified in
the notice, the permittee shall submit a written time schedule to the Director for
modifying the site to meet minimum requirements. The permittee shall provide
copies of revised plans and certification in writing to the Director that the changes
have been made.
The stormwater management system shall be constructed in its entirety, vegetated
and operational for its intended use prior to the construction of any built -upon
surface.
6. The runoff from all built -upon area within the drainage area of the pocket of high
density permitted stormwater system must be directed into the permitted
stormwater control system.
Page 2 of 7

State Stormwater Permit
Permit No. SW6090902
Within the low density portions of the permitted project, all roof drains shall
terminate at least 30 feet from the mean high water mark of surface waters.
The permittee shall submit to, the Director and shall have received approval for
revised plans, specifications, and calculations prior to construction, for any
modification to the approved plans, including, but not limited to, those listed below:
a. Any revision to the approved plans, regardless of size.
b. Project name change.
C. Transfer of ownership.
d. Redesign or addition to the approved amount of built -upon area.
e. Furthersubdivision, acquisition, or sale of all or part of the project area. The
project area is defined as all property owned by the permittee, for which
Sedimentation and Erosion Control Plan approval or a CAMA Major permit was
sought.
f. Filling in, altering, or piping of any vegetative conveyance shown on the
approved plan.
9. The Director may determine that other revisions to the project should require a
modification to the permit.
10. All stormwater collection and treatment systems must be located in either dedicated
common areas or recorded easements. The final plats for the project must be
recorded showing all such required easements, in accordance with the approved
plans.
11; During'construction, erosion shall be kept to a minimum and any eroded areas of the
system will be repaired immediately.
12. Upon completion of construction, prior to issuance of a Certificate of Occupancy, and
prior to operation of this permitted facility, a certification must be received from an
appropriate designer for the system installed certifying that the permitted facility has
been installed in accordance with this permit, the approved plans and specifications,
and other supporting documentation. Any deviations from the approved plans and
specifications must be noted on the Certification.
13. If the stormwater system was used as an Erosion Control device, it must be restored
to design condition prior to operation as a stormwater treatment device, and prior to
occupancy of the facility.
14. Permanent seeding requirements for the stormwater control must follow the
guidelines established in the North Carolina Erosion and Sediment Control Planning
and Design Manual.
15. This permit shall become void unless the facilities are constructed in accordance with
the conditions of this permit, the approved plans and specifications, and other
supporting data.
16. The permittee shall at all times provide the operation and maintenance necessary to
assure that all components of the permitted stormwater system function at optimum
efficiency. The approved Operation and Maintenance Plan must be followed in its
entirety and maintenance must occur at the scheduled intervals including, but not
limited to:
a. Semiannual scheduled inspections (every 6 months).
b. Sediment removal.
c. . Mowing and re -vegetation of side slopes.
d. Immediate repair of eroded areas.
Page 3 of 7

State Stormwater Permit
Permit No. SW6090902
e. Maintenance of side slopes in accordance with approved plans and
specifications.
f. Debris removal and unclogging of structures, orifice, catch basins and piping.
g. Access to all components of the system must be available at all times.
17. Records of maintenance activities must be kept by the permittee. The records will
indicate the date, activity, name of person performing the work and what actions
were taken.
18. The permittee shall submit to the Division of Water Quality an annual summary
report df the maintenance and inspection records for each BMP. The report shall
summarize the inspection dates, results of the inspections, and the maintenance
work performed at each inspection.
19. Prior to transfer of the permit, the stormwater facilities will be inspected by DWQ
personnel. The facility must be in compliance with all permit conditions. Any items
not in compliance must be repaired or replaced to design condition prior to the
transfer. Records of maintenance activities performed to date will be required.
20. Prior to the sale of any lot, the following deed restrictions must be recorded:
a. The following covenants are intended to ensure ongoing compliance with
State Stormwater Management Permit Number SW6090902, as issued by the
Division of Water Quality under the stormwater rules.
b. The State of North Carolina is made a beneficiary of these covenants to the
extent necessary to maintain compliance with the Stormwater Management
Permit.
C. These covenants are to run with the land and be binding on all persons and
parties claiming under them.
d. The covenants pertaining to stormwater may not be altered or rescinded
without the express written consent of the State of North Carolina, Division of
Water Quality.
e. Alteration of the drainage as shown on the approved plans may not take place
without the concurrence of the Division of Water Quality.
f. The maximum built -upon area per lot is 3,100 square feet. This allotted
amount includes any built -upon area constructed within the lot property
boundaries, and that portion of the right-of-way between the front lot line and
the edge of the pavement. Built upon area includes, but is not limited to,
structures, asphalt, concrete, gravel, brick, stone, slate, coquina and parking
areas, but does not include raised, open wood decking, or the water surface of
swimming pools.
g. Built -upon area in excess of the permitted amount will require a permit
modification.
21. A copy of the recorded deed restrictions must be submitted to the Division within 30
days of the date of recording the plat, and prior to selling lots. The recorded copy
must contain all of the statements above, the signature of the Permittee, the deed
book number and page, and the stamp/signature of the Register of Deeds.
22. Decorative spray fountains will be allowed in the stormwater treatment system,
subject to the following criteria:
a. The fountain must draw its water from less than 2' below the permanent pool
surface.
b. Separated units, where the nozzle, pump and intake are connected by tubing,
may be used only if they draw water from the surface in the deepest part of the
pond.
C. The falling water from the fountain must be centered in the pond, away from
the shoreline.
d. The maximum horsepower for the fountain's pump is 1/6 HP.
Page 4 of 7

State Stormwater Permit
Permit No. SW6090902
III. GENERAL CONDITIONS
This permit is not transferable to any person or entity except after notice to and
approval bythe Director. In the event there is either a desire for the facilities to
change ownership, or there is a name change of the Permittee; a completed
"Name/Ownership Change Form" must be submitted to the Division of Water Quality,
signed by the parties involved, along with the applicable documents as listed on page
2 of the form. The project must be in good standing with DWQ. The approval of this
request will be considered on its merits and may or may not be approved.
The permittee is responsible for compliance with all of the terms and conditions of
this permit until such time as the Director approves the transfer request.
3. Failure to abide by the conditions and limitations contained in this permit may
subject the Permittee to enforcement action by the Division of Water Quality, in
accordance with North Carolina General Statute 143-215.6A.to 143-215.6C.
4. The issuance of this permit does not preclude the Permittee from complying with any
and all statutes, rules, regulations, or ordinances, which may be imposed by other
government agencies (local, state, and federal), which have jurisdiction.
5. In the event that the facilities fail to perform satisfactorily, including the creation of
nuisance conditions, the Permittee shall take immediate corrective action, including
those as may be required by this Division, such as the construction of additional or
replacement stormwater management systems.
6. The permit may be modified, revoked and reissued or terminated for cause. The
filing of a request for a permit modification, revocation and re -issuance or
termination does not stay any permit condition.
7. Permittee grants permission to staff of the DWQ to access the property for the
purposes of inspecting the stormwater facilities during normal business hours.
8. Approved plans and specifications for this project are incorporated by reference and
are enforceable parts of the permit.
9. The permittee shall notify the Division in writing of any name, ownership or mailing
address changes within 30 days.
10. A copy of the approved plans and specifications shall be maintained on file by the
Permittee for a minimum of ten years from the date of the completion of
construction.
11. The permittee shall submit a renewal request with all required forms and
documentation at least 180 days prior to the expiration date of this permit.
Permit issued this the 2nd day of November 2009.
NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION
c
forColeen H. Sullins, Director
Division of Water Quality
By Authority of the Environmental Management Commission
Page 5 of 7

State Stormwater Permit
Permit No. SW6090902
Camden Wood Subdivision, Section 3 Page 1 of 2
Stormwater Permit No. SW6090902
Cumberland County
Designer's Certification
I, as a duly registered in the State of North
Carolina, having been authorized to observe (periodically/weekly/full time) the construction
of the project,
(Project)
for (Project Owner) hereby state that, to the best of my
abilities, due care and diligence was used in the observation of the project construction such
that the construction was observed to be built within substantial compliance and intent of
the approved plans and specifications.
The checklist of items on page 2 of this form is a part of this Certification
Noted deviations from approved plans and specifications:
Signature
Registration Number
Date
SEAL
Page 6 of 7

State Stormwater Permit
Permit No. SW6090902
Certification Requirements:
Page 2 of 2
_1. The drainage area to the system contains approximately the permitted
acreage.
_2. The drainage area to the system contains no more than the permitted amount
of built -upon area.
3. All the built -upon area associated with the project is graded such that the
runoff drains to the system.
4. All roof drains are located such that the runoff is directed into the system.
_5. The outlet/bypass structure elevations are per the approved plan.
6. The outlet structure is located per the approved plans.
7. Trash rack is provided on the outlet/bypass structure.
8. All slopes are grassed with permanent vegetation.
_9. Vegetated slopes are no steeper than 3:1.
10. The inlets are located per the approved plans and do not cause short-
circuiting of the system.
11. The permitted amounts of surface area and/or volume have been provided.
12. Required drawdown devices are. correctly sized per the approved plans.
_13. All required design depths are provided.
_14. All required parts of the system are provided, such as a vegetated shelf, a
forebay, and the vegetated filter.
15. The required dimensions of the system are provided, per the approved plan.
cc: NCDENR-DWQ Regional Office
Inspector, Cumberland County Building Inspections
Page 7 of 7

5"i, C 4 20M
ALLEN-ALLEN & ASSOCIATES of N.C., P.A.
Engineers, Land Planners & Surveyors
2606 Raeford Road, Suite 31 [phone] (Phone)
Fayetteville, N.C. 28303 [phone] (Fax)
CAMDEN WOODS SUBDIVISION, SECTION THREE
Wet Detention Basin Calculations

ALLEN-ALLEN & ASSOCIATES of N.C., P.A.
Engineers, Land Planners & Surveyors
2606 Raeford Road, Suite 31 [phone] (Phor
Fayetteville, N.C. 28303 [phone] (Fax)
TABLE of CONTENTS
Camden Wood Subdivision, Section 3 - Wet Detention Basin
ME
- Objective.........................................................................................................I
- Approach.........................................................................................................1
- Design Constraints..........................................................................................I
- Given Parameters............................................................................................2
- Compute Routing Parameters.........................................................................3
Pre-Construction.................................................................................3-4
Post-Construction...............................................................................4
- Table-1: Permanent Pool Stage -Storage Table (Main Pool)..........................5
- Table-2: Permanent Pool Stage -Storage Table (Forebay) ..............................5
- Check % Forebay @ Permanent Pool Level..................................................5
- Check Average Depth @ Permanent Pool Level...........................................5
- Table-3 Temporary Pool Stage -Storage Table (Perm Pool - Top of Shelf) ... 6
- Table-2: Routing - Stage -Storage Table (Above the Top of Shelf)...............6
- Permanent Pool Dimensions..........................................................................6
- Calculation for Required Surface Area at Permanent Pool)..........................6
- Calculation for Treatment Volume/Elevation (Temporary Pool)..................7
- Outlet Orifice Structure Calculations............................................................7-8

ALLEN-ALLEN & ASSOCIATES of N.C., P.A.
Engineers, Land Planners & Surveyors
2606 Raeford Road, Suite 31 [phone] (Phor
Fayetteville, N.C. 28303 [phone] (Fax)
October 1, 2009
Camden Wood Subdivision, Section 3 - Wet Detention Basin Calculations
Objective:
Design a Wet Detention Basin to Control and Treat the first 1 " of runoff.
Approach:
Determine the dimensions of the Permanent Pool:
Iterate Basin Dimensions; calculate Average Depth, Surface Area and Forebay
Volume to Determine Final Basin Dimensions that are supported by the Design
Constraints.
Determine the Temporary Pool Height, to Allow Storage of the Treatment Volume:
Calculate the Required Treatment Volume and subsequent Stage.
Determine the Outlet Structure Characteristics:
Calculate Allowable Draw -Down Outflow Rate;
Design the Orifice that will Meet the Allowable Draw -Down Time;
Determine the Maximum Stage by Routing the Basin with the 25 Year Storm;
Set the Primary Spillway;
Determine the Velocity Dissipaters for the Inflow and Outflow Rates for Erosion
Control purpose's.
Design Constraints:
Design is in Accordance with the "NCDENR Stormwater BMP Manual".
Minimum Average Depth: 3.0'
90% Removal of Total Suspended Solids (Piedmont Region) - Table 10-3.
Forebay Volume at the Permanent Pool to be Approximately 20% of the Total Volume of
the Basin (including Forebay Volume) at the Permanent Pool.
Draw -Down Rate not to Exceed the Pre -Construction, 1 Year - 24 Hour Storm.
The Rational Method is used to Calculate the Outflow Rate.
I

Given:
Location: Cumberland County, NC
Drainage Area to Wet Detention Basin = 8.83 Acres
Area of Proposed & Offsite Houses (including patio, drive, shed, sidewalk from drive to
house) = approximately 3100 sf (0.07 Acres) (data provided by Developer, Charles Gore).
Total Area Contributing (Onsite + Offsite) to the Wet Detention Basin = 384,635 sf
(8.83 Acres)
Total Impervious Area (Onsite + Offsite) to the Wet Detention Basin = 129,373 sf
(2.97 Acres)
Percent Impervious (Onsite) Area to the Wet Detention Basin = 33.64%
Remaining Onsite Area off ends of Cul-de-Sac(s) (and Finger at the most Northwestern
portion of Property) = 374,180 sf (8.59 Acres)
Impervious Area off ends of Cul-de-Sac(s) (and Finger at the most Northwestern portion
of Property) = 27,900 sf (0.64 Acres)
Percent Impervious Area off ends of Cut-de-Sac(s) (and Finger at the most
Northwestern portion of Property) = 7.46%
Main Basin Bottom Elevation: 162.5'
Main Basin Sediment Storage Bottom Elevation: 161.5'
Forebay Bottom Elevation: 163.5'
Forebay Basin Sediment Storage Bottom Elevation: 162.5'
Bottom of Shelf (BS) Elevation: 168.5'
Permanent Pool (PP) Elevation: 169.0'
Top of Shelf (TS) Elevation:169.5'
Temporary Pool Elevation: 169.67.
2

Compute Routing Parameters:
Soil Types: NoA - Norfolk Hydrologic Group "B"
BbB - Blaney Hydrologic Group `B"
Use Cn (perv) = 61 (> 75% grass cover) Good Condition
Cn (imp) = 100
Cn(comp) = ((0.336 x 8.83 x 100) + (0.664 x 8.83 x 61))/8.83 = 74.1
S = (1000/Cn) - 10 = 3.50
P = 3.93 in (10 yr - 6 hr) Precipitation
Q* = ((P - (0.2S))^2)/(P+(0.8S)) =1.55 in(10 yr - 6 hr) Runoff Depth
I (1 yr/5 min) = 5.21 in/hr
1(2 yr/5 min) = 6.11 in/hr
1(10 yr/5 min) = 7.92 in/hr
I (25 yr/5 min) = 8.89 in/hr
I (50 yr/5 min) = 9.60 in/hr
I (100 yr/5 min) = 10.30 in/hr
I (1 yr/24 hr) = 0.13 in/hr
Pre -Construction:
Q(pre) = CIA
Area (Total for Wet Detention Basin) = 8.83 ac
C(pre-comp) = 0.17
M

Pre -Construction (cont.)
Q (1 yr/5 min) = 7.82 cfs
Q (2/5) = 9.17 cfs
Q (1015) = 11.89 cfs
Q (25/5) = 13.34 cfs
Q (50/5) = 14.41 cfs
Q (100/5) = 15.46 cfs
Q (1 yr/24 hr) = 0.20 cfs
Post -Construction:
Q(post) = CIA
Area (Total for Wet Detention Basin) 8.83 ac
Impervious Area = 2.97 ac
Pervious Area = 5.86 ac
C (grass) - 0.15 (Lawns, heavy soil, < 2%)
C(impervious) = 1.0
C(post-comp) = 0.44
Qp (I yr/5 min) = 20.24 cfs
Qp (2/5) = 23.74 cfs
Qp (10/5) = 30.77 cfs
Qp (25/5) = 34.54 cfs
Qp (5015) = 37.30 cfs
Qp (100/5) = 40.02 cfs
Q (I yr/24 hr) = 0.51 cfs
Tp = Vol = (Q* x A)/(1.39 x Qp)
Tp (1 yr/5 min) = 29.43 min
Tp (2/5) = 25.09 min
Tp (10/5) = 19.36 min
Tp (25/5) = 17.25 min
Tp (50/5) = 15.97 min
Tp (100/5) = 14.89 min
4

Table-1: Permanent Pool State -Storage Table (Main Basin)
Incr
Accum
Contour
Area
Volume
Volume (S)
169.0 (PP)
9583
4268
36339
168.5 (BS)
7488
7104
32071
167.5
6719
6351
24967
166.5
5983
5635
18616
165.5
5286
4956
12981
164.5
4626
4315
8025
163.5
4003
3710
3710
162.5
3417
0
0
Table-2: Permanent Pool Stage -Storage Table (Forebay Basin)
Incr
Accum
Contour
Area
Volume
Volume (S)
169.0 (PP)
2770
1334
9699
168.5 (BS)
2567
2373
2373
167.5
2178
1992
1992
166.5
1806.
1639
4000
165.5
1472
1322
2361
164.5
1039
1039
1039
163.5
905
0
0
Check % Forebay (a, Permanent Pool Level:
(Volume Forebay) / Volume (Forebay + Main Pool)) x 100 = (9699 /(9699 + 36339)) x 100
21.07% Good
Check Average Depth (a) Permanent Pool Level:
(Total Permanent Pool Volume) / (Total Permanent Pool Area) =
(9699 + 36339) / (2770 + 9583) = 3.73 > 3.0 Good
5

Table-3: Temporary Pool Stage -Storage Table (Permanent Pool - Top of Shell)
Inc.
Accum.
Contour
Area
Volume
Volume (S)
Stage Z
169.5 (TS)
15593
1522
6959
0.5
169.4
14856
1454
5437
0.4 (2)
169.3
14214
1390
3983
0.3
169.2
13583
1327
2593
0.2
169.1
12963
1266
1266
0.1 (1)
169.0 (PP)
12353
0
0
0.0
b = 1.05
k(s) = 14,230
Table-4. Routing - Stage -Storage Table (Above the Top of She1Q
Incr
Accum
Contour
Area
Volume
Volume (S)
Stage Z
174.5
25825
24767
110285
5 (2)
173.5
23708
22667
85518
4
172.5
21626
20620
62851
3
171.5
19613
18641
42231
2
170.5
17668
16631
23590
1 (1)
169.5 (TS)
15593
6959
6959
0
b = 0.96
k(s) = 23,524
Permanent Pool Dimensions (Included Forebay):
60' x 200'
Calculate Required Surface Area for the Wet Detention Basin from Table 10-3
Interpolating with an Average Depth of 3.73, and a % Impervious of 33.64%, gives a SA/DA =
1.94;
Drainage Area = 8.83 Acres
Permanent Pool Surface Area Required = 7,462 sf;
12,353 sf Provided > 7,462 sf Required Good
6

Calculate Treatment Volume (Temporary Pool) Volume:
Treatment Volume: 3630 x R(D) x R(V) x A
R(V) = 0.05 + (0.9 x I(A))
I(A) = 33.64%
R(V) = 0.35
R(D) = 1 "
A = 8.83 acres
Temporary Treatment Volume = 11,306 cf
See Table 3: Temporary Pool Stage -Storage Table
Treatment Volume between Permanent Pool and the Top of Shelf= 6,959 cf
Excess Treatment Volume above the Temporary Shelf = 11,306 - 6,959 = 4,247 cf
See Table 4: Routing Parameters
Reformulating the Stage -Storage Formula: Z = ((S/k(s))^1/b), b = 0.96, k(s) = 23,524
Depth for the Excess Treatment Volume above the Temporary Shelf = 0.17
Temporary Pool Elevation = 169.5 + 0.17=169.67'
Outlet Orifice Structure:
Allowable Outflow Rate:
Q (pre) (1 yr/24 hr) = 0.39 cfs
Draw -Down Volume = 11,219 cf
Full Depth of Temporary Pool = Temporary Pool Elevation - Permanent Pool Elevation =
169.67 - 169.0 = 0.67
ho = h/3, h = Riser Crest Elevation - Permanent Pool Elevation = 171.15' - 169.0' = 2.15'
ho = 2.15/3 = 0.72
Orifice Equation: Q = C(D) x A x (2gh)^%:
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Solve for Q: Try d =1.5"
Q = 0.0503 < 0.20 cfs Good
Draw -Down Time for 11,306 cf at 0.0503 = 2 days -14.4 hours
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